A system using a magneto-optic recording material desirably produces a magnetic field having a component perpendicular to the recording layer at the location where the light beam is focused. A conventional magnetic head used in such magneto-optical recording is constructed by winding a coil around a magnetic core. The coil around the magnetic core is used for generating the magnetic field. A large coil is often undesirable for generating high frequency recording, since large coil inductance prohibits changes of current at a desired high data rate.
The bottom surface of a near-field lens can be etched, ion- milled or cut away to form a mesa-like structure and allow a magnetic coil to be formed about the focused beam. This operation is described in PCT Publication No. 817,315. Generally, the width of the rectangle is narrow, but the length is long enough to include the field-of-view of the near field lens so that the maximum tracking range is available by steering the beam along the length of the mesa structure. The structure also should be thick enough to allow winding of a coil having one or more turns. It is also useful for the mesa to extend below the level of the coil to avoid the coil interfering with the air bearing surface of the slider.
Multiple layers of coils may be used to increase the magnetic efficiency. The typical magnetic field to change the magnetic state of the magneto-optical medium is approximately in a range from 80 to 300 Oersteds.